Abstract: A method and device are provided for fast impedance measurement of a biological object having dynamically varying in time parameters, wherein a titlet shaped pulse is introduced into the object and a voltage response signal is measured and analyzed by a processing unit for estimating the impedance of the object. The titlet pulse has a start frequency substantially in one end of the frequency range of interest and a stop frequency substantially in the other end of the frequency range of interest and a duration of the titlet pulse is one cycle or less.

Abstract: Mechanical oscillators employ the use of resonance parameters, frequency and the quality factor Q, for the measurement of corrosion or deposition. The ability of a mechanical oscillator to measure small amounts of metal loss or deposition is not only dependent upon the mechanical design but is limited by the precision in determining the resonance frequency and Q. Methods for measuring these resonance parameters with a high precision in the presence of noise are provided. The increased degree of precision improves the utility of these devices as sensitive probes for corrosion and deposition (fouling) measurement. The increased degree of precision is enabled in part by employing curve fitting consistent with modeling the mechanical oscillator as a simple harmonic oscillator. This curve fitting procedure, combined with averaging and utilizing signal processing parameters to mitigate noise effects, adds precision in measuring resonance parameters.

Abstract: A method of estimating the time of flight of a burst signal includes: receiving the burst signal; determining the slope of the phase characteristic of the Fourier transform of the received burst signal; and estimating the time-of-flight of the burst signal from the slope of the phase characteristic of the Fourier transform of the received burst signal.

Abstract: A method of isolating a frequency in a rotating machine having at least one sensor includes receiving, from the at least one sensor, a sensor signal that includes at least one frequency, converting the sensor signal to a digital vibration signal, modifying the vibration signal to generate an envelope signal, synchronously oversampling the envelope signal to generate a synchronous envelope signal, and transforming the synchronous envelope signal into a frequency spectrum to isolate the frequency.

Abstract: Embodiments relate systems and methods for detecting machine faults in a network using acoustic monitoring. In embodiments, one or more servers, clients, or other machines in a managed network can have a microphone or other acoustic sensor integrated into motherboard or other hardware. The sensor can sample acoustic signals from inside or near the machine, and can digitize that data. The resulting set of acoustic data can be transmitted to a management server or other destination for analysis of the operating sounds related to that machine. For instance, the acoustic data can be analyzed to detect indications of a failed or failing hard drive, for instance by detecting spindle whine or head movement noises, or a failed or failing power supply based on other sounds. The management server can respond to potential fault events for instance by issuing configuration commands, such as instructions to power down the malfunctioning component.

Abstract: The condition of a structure using remote interrogation of a multi-state passive wireless antenna sensor that has a known resonant frequency when mounted on the structure. The passive wireless antenna sensor is connected to a remotely operated switching circuit that includes a photocell. An interrogation system transmits a series of radio frequency signals with sweeping frequencies around the known resonant frequency to the passive wireless antenna sensor, while simultaneously pulsing a laser to switch the passive wireless antenna sensor between a first state and a second state in which it is exposed to open-circuit or short-circuit conditions. A signal is reflected from the passive wireless antenna sensor in each of the first and second states, and a resonant frequency of the passive wireless antenna sensor is determined by normalizing the received signals to isolate the antenna mode.

Abstract: A pre-channelized spectrum analyzer utilizes a channelizer as a preprocessor for parallel-configured low-resolution spectrum analyzers so as to perform as a high resolution spectrum analyzer. The pre-channelized spectrum analyzer has a polyphase filter that channelizes a signal input and an IFFT that generates filter bank outputs derived from the channelized signal. Spectrum analyzers are in communications with the filter bank outputs so as to generate a spectral decomposition of a subset of those outputs. The spectrum analyzers each perform a window and an FFT function on a corresponding one of the filter bank subset.

Abstract: A method for distinguishing a signal of interest from one or more interference signals in a received analog signal comprises receiving an analog signal at a radio front end, and transmitting the received analog signal to an analog-to-digital converter to sample data in the received analog signal and output a digital signal. A sub-channel Fast Fourier Transform (FFT) is performed on the digital signal, and sub-channel FFT bin magnitudes are averaged over a set period of time to determine a shape of the received signal. The shape of the received signal is compared to one or more signal reference patterns by computing a metric for the shape of the received signal, and computing a metric for the one more signal reference patterns. The computed metrics are then compared to a predetermined threshold value to determine the presence, or lack thereof, of a signal of interest in the received signal.

Abstract: A waveform acquiring unit acquires a time waveform of an electromagnetic wave. The time waveform is decomposed into wavelet expansion coefficients by wavelet transform. Influence levels of the respective wavelet expansion coefficients to a spectrum are calculated. The wavelet expansion coefficients are weighted based on at least the influence levels of the wavelet expansion coefficients to the spectrum. The weighted wavelet expansion coefficients are converted into time waveforms by inverse wavelet transform. Thus, the time waveforms that holds spectrum information needed for spectroscopic analysis and has a reduced noise is provided.

Abstract: A method for assessing the integrity of a rock mass, the method including impacting the rock mass, capturing an acoustic signal generated as a result of the impact, deriving a frequency distribution for the captured acoustic signal, processing data from the frequency distribution by means of a neural network process applying artificial intelligence to assess the inputted data, and presenting a signal from the neural network process which is indicative of the integrity of the rock mass.

Abstract: Some embodiments of the present invention provide a system that controls a device that generates vibrations in a computer system. During operation, a critical vibration frequency is determined for the computer system. Next, a keep-out zone is generated based on the critical vibration frequency, wherein the keep-out zone specifies a range of frequencies to be avoided. Then, the device is controlled based on the keep-out zone to reduce vibrations generated by the device in the keep-out zone.

Abstract: The apparatus corrects multi-phase signals for detecting a position of an object and obtains a phase corresponding to the position of the object. The apparatus includes a correcting unit correcting the multi-phase signals with error coefficients, respectively, a phase calculating unit performing calculation for the corrected multi-phase signals to obtain the phase, a regression unit performing regression for the calculated phases to obtain reference phases, a Fourier transform unit respectively performing Fourier transform for the corrected multi-phase signals whose phases having been respectively changed into the reference phases, and an updating unit updating, using Fourier coefficients obtained by the Fourier transform unit, the error coefficients respectively corresponding to the Fourier coefficients. The updating unit updates the error coefficients if a regression error in the regression performed by the regression unit satisfies a predetermined condition.

Abstract: Embodiments of a system that determines a condition associated with an integrated circuit disposed on a circuit board are described. During operation, the system receives electromagnetic-interference (EMI) signals from one or more antennas while the integrated circuit is operating, where the one or more antennas are disposed on the circuit board. Then, the system analyzes the received EMI signals to determine the condition.

Abstract: A real-time trigger figure-of-merit indicator for test and measurement instruments provides an indication of how close a signal-under-test is to satisfying a relevant trigger condition. The indicator includes a first marker that indicates a real-time trigger figure-of-merit that is calculated based on digital samples that represent the signal-under-test, and a second marker that indicates a level that the figure-of-merit must exceed in order for a trigger event detector to detect a trigger event and generate a trigger signal. Thus, by observing the indicator, a user may easily ascertain how close a signal-under-test is to satisfying the relevant trigger condition without requiring the instrument to actually trigger.

Abstract: In one embodiment, an apparatus comprises a nano-scale spectrum sensor configured to be electromagnetically excitable at a predetermined frequency based on received ambient electromagnetic radiation. The apparatus is also configured to be able to use this excitation of the nano-scale spectrum sensor to thereby determine ambient electromagnetic radiation spectrum usage.

Abstract: A method for determining an optimum sampling frequency to be performed by a power analyzer includes the following computer-implemented steps: sampling a time domain signal to obtain a sampling signal according to a predetermined sampling frequency; obtaining two reference sampling signals using higher and lower sampling frequencies compared to the predetermined sampling frequency; transforming the sampling signal and the reference sampling signals to frequency domain signals; computing a sum-of-amplitudes for each of the three frequency domain signals; estimating a minimum sum-of-amplitudes value and a corresponding re-sampling frequency; obtaining a new reference sampling signal using the re-sampling frequency; transforming the new reference sampling signal to a frequency domain signal, and computing a sum-of-amplitudes therefor; and re-estimating the minimum sum-of-amplitudes value and the corresponding re-sampling frequency.

Abstract: A method of calibrating a robotic device, such as a cardiac catheter, includes oscillating the device on an actuation axis by applying an oscillation vector at an oscillation frequency. While oscillating, a location of the device is periodically measured to generate a plurality of location data points, which may express the location of the device relative to a plurality of measurement axes. The location data points are then processed using a signal processing algorithm, such as a Fourier transform algorithm, to derive a transfer function relating a position of the device to a movement vector for the actuation axis. The transfer function may be resolved into and expressed as a calibration vector for the actuation axis, which may include one or more components, including zero components, directed along each of the measurement axes. The process may be repeated for any actuation axes on which calibration is desired.

Abstract: Light to be measured L and sampling pulse light LSP are each split into M beams, and a time delay of 0, T, 2T, . . . , (M?1)T is given to each of the M-split sampling pulse light beams. The M-split light beams to be measured are then respectively multiplexed with M optical 90-degree hybrids, and M electrical field amplitudes per time T are determined for the light beam to be measured, based on M sets of output currents received at a balance light receiving element that receives light emitted from each of the optical 90-degree hybrids. The amplitudes of the respective wavelength optical signals contained in the light beam to be measured are calculated through Fourier transformations of the field electrical amplitudes. Pulsed light with a spectral width that covers the total frequency bandwidth of the light to be measured is used as the sampling pulse light.

Abstract: Using a mechanical shaker test the shear wavespeed in a plate is estimated by applying a cyclical point force to the plate, measuring normal velocity of waves caused by the force, transforming temporal domain measurements with a Fourier transform into a frequency domain, transforming spatial domain measurements into a {kx,ky} wavevector domain spectra using Fourier transforms, determining propagation wavenumbers for given Lamb waves from peaks within the {kx,ky} spectra, and determining shear wavespeed by applying a Newton-Raphson gradient method using the propagation wavenumbers to Raleigh-Lamb dispersion curve equations.

Abstract: There is provided with a method of identifying a frequency response of a controlled object at a sampling period of control input in a multiplexed-input multirate system in which a sampling period of control output is even “P” multiples of the sampling period of control input wherein the control object is represented by FIR filter, an M-series signal corresponding to an acquisition data length Mp×P?1 is generated, the Mp indicates a period of the M-series signal, an impulse response value of the controlled object is estimated based on the M-series signal and output data outputted from the controlled object by inputting the M-series signal thereto, and the frequency response of the controlled object is identified by performing a discrete Fourier transform on the impulse response value.

Abstract: A device for machine diagnostics, with a vibration sensor (12) for detecting vibration signals on the machine (10), a unit (14) for conditioning the vibration signals, an A/D converter (16) for digitizing the conditioned vibration signals, a data processing unit (20) for splitting the digital signals into at least two frequency ranges, the data processing unit being made to scale the signal for each frequency range to an amplitude resolution which is less than the amplitude resolution of the A/D converter, and an evaluation unit (30) for further evaluation of the split signals.

Abstract: An oscillating frequency drift detecting method, which comprises: receiving an oscillating signal with an oscillating frequency, wherein the oscillating signal is generated by a crystal oscillator; generating a self-mixing signal according to the oscillating signal; obtaining a self-mixing frequency of a maximum power of the self-mixing signal in a specific frequency range; and computing a frequency drift of the oscillating frequency, according to the self-mixing frequency of the maximum power, and the oscillating frequency.

Abstract: A method of prognosing a mechanical system to predict when a failure may occur is disclosed. Measurement data corresponding to the mechanical system is used to extract one or more features by decomposing the measurement data into a feature space. A prediction model is then selected from a plurality of prediction models for the one or more features based at least on part on a degradation status of the mechanical system and a reinforcement learning model. A predicted feature space is generated by applying the selective prediction model to the feature space as well as a confidence value by comparing the predicted feature space with a normal baseline distribution, a faulty baseline distribution, or a combination thereof. A status of mechanical system based at least in part on the confidence value is then provided.

Abstract: A method of wirelessly interrogating a sensing device comprising a plurality of passive sensors, to determine a measurement parameter, comprises the steps of repeatedly interrogating the sensing device using a predetermined transmission signal and detecting the response; estimating the measurement parameter for each sensor by means of an analysis of the data accumulated as a result of the interrogation step, and determining the average of the parameters derived from the estimating step for each sensor, using a weighted average, in which the weightings depend on the amplitude of the sensor response. The measurement parameter may be a resonant frequency where the passive sensors are resonant devices, and the sensors may be SAW devices.

Abstract: A signal analyzing system is provided. The signal analyzing system includes a band pass filter (BPF), a sampling unit and a continuous shifted transform (CST) unit. The BPF filters an input signal to obtain a filtered signal. The sampling unit samples the filtered signal to obtain a discrete signal according to a sampling frequency. The CST unit obtains a first frequency spectrum according to the N discrete signals that are sampled continuously, and obtains a second frequency spectrum according to a (N+1)th discrete signal and the first frequency spectrum. Each of the first and second spectra includes N Fourier transform operation results.

Abstract: Embodiments of the invention provide multi-channel OCT (Optical Coherence Tomography) for imaging biological tissue or the like, and for temperature and/or force sensing, preferably in real time. In one embodiment, an optical signal processing system comprises: a processor; a memory; a receiving module to receive in real time input from multiple channels of OCT producing interfering optical signals representing multiple measured distances for a target imaging object; a Fast Fourier Transform (FFT) module to apply FFT on the interfering optical signals in real time to produce Fourier frequencies corresponding to the multiple measured distances; and a calculation module to calculate in real time multiple force components of a force applied on the target imaging object to cause at least some of the multiple measured distances for the target imaging object based on the Fourier frequencies from the FFT module.

Abstract: A method and system for detecting a signal source at a specified frequency in the presence of background noise includes a processor; a first sensor mounted at a first location operatively connected to the processor; a second sensor mounted at a second location operatively connected to the processor; the processor operating to compute the amplitudes of the first and second Fourier transforms of the outputs of the first and second sensors, respectively, the difference in the amplitudes of the first and second Fourier transforms being determinative of the existence of a signal being generated at the predetermined frequency.

Abstract: A frequency offset estimating apparatus includes an nth power computing module and a spectrum analyzing module. By raising a received signal to nth power to generate an nth power signal and analyzing the spectrum of the nth power signal, the present invention is capable of quickly and accurately estimating a frequency offset of the received signal. As being unaffected by channel characteristics, the estimating frequency offset apparatus is suitable for all channel environments.

Abstract: An apparatus is provided for measuring a frequency-domain optical coherence tomography power spectrum from a sample. The apparatus includes a partially reflective element configured to be optically coupled to a light source and to the sample. A first portion of light from the light source is configured to be reflected by the partially reflective element. A second portion of light from the light source is configured to propagate through the partially reflective element, to impinge the sample, and to reflect from the sample. The apparatus is configured to receive the first and second portions of light and to measure the frequency-domain optical coherence tomography power spectrum in response to the first portion of light and the second portion of light.

Abstract: A method for dynamic cerebral autoregulation (CA) assessment includes acquiring a blood pressure (BP) signal having a first oscillatory pattern from a first individual, acquiring a blood flow velocity (BFV) signal having a second oscillatory pattern from the first individual, decomposing the BP signal into a first group of intrinsic mode functions (IMFs), decomposing the BFV signal into a second group of IMFs, determining dominant oscillatory frequencies in the first group of IMFs, automatically selecting a first characteristic IMF from the first group of IMFs that has its associated dominant oscillatory frequency in a predetermined frequency range, automatically selecting a second characteristic IMF from the second group of IMFs, calculating a time sequence of instantaneous phase difference between the first characteristic IMF and the second characteristic IMF, computing an average of the instantaneous phase difference in the time sequence, and identifying a pathological condition in the first individual.

Abstract: System and method implementations for testing a cooling fan in an electronic device are disclosed. As one example, a method of testing a cooling fan of a sample electronic device is disclosed that includes generating an audio input at an audio speaker and receiving an audio output at an audio microphone to obtain an audio output signal. The method further includes processing the audio output signal to identify frequency modulation in the audio output signal, and identifying a state of motion of fan blades of the cooling fan based, at least in part, on the frequency modulation.

Abstract: A moored buoy floating at the ocean surface and anchored to the seafloor precisely measures acceleration, pitch, roll, and Earth's magnetic flux field of the buoy over a limited sampling period.

Abstract: A system and method for measuring the frequency response of a system under test using a single swept-frequency chirp signal. A tapered chirp-frequency test signal is created with a bandwidth defined by first and second frequencies. The test signal is routed to a calibration path, and the output of the calibration path is routed to a digitizer. The output of the calibration path is digitized, and a Fourier transform of the calibration path output is generated. The test signal is then routed to a test system, and the output of the test system is coupled to the digitizer. The output of the test system is digitized, and a Fourier transform of the test system output is generated. A normalized frequency-domain representation of the test system created by dividing the Fourier transform of the test system output by the Fourier transform of the calibration path output.

Abstract: Aspects of a method and system for detecting Bluetooth signals utilizing a wideband receiver are provided. In this regard, a portion of a frequency band may be scanned multiple times, where each scan comprises receiving signals present in the scanned portion of the frequency band. Based on results of a Fast Fourier Transform performed on the received signals, presence of one or more Bluetooth transmissions in the received signals may be detected. In instances that a Bluetooth transmission is detected, a type of the Bluetooth transmission may be determined based on a number of the scans in which the Bluetooth transmission was detected. In instances that a detected Bluetooth transmission is a page, a Bluetooth transceiver in the wireless communication device may be powered up and/or enter a page scanning mode. The scans may be performed by a wireless local area networking receiver within the wireless communication device.

Abstract: This invention relates to a method of, and a system for, monitoring electromagnetic interference. The method comprising capturing a plurality of time domain waveforms, and a plurality of scatter plots; receiving the plurality of captured time domain waveforms and scatter plots; applying a fast fourier transform (FFT) to each of the received time domain waveforms as it is received thereby to receive FFT outputs; storing the FFT outputs in a database; generating a statistically representative spectrograph or spectrogram in the frequency domain based on at least the stored FFT outputs and scatter plots or data associated with the scatter plots, combining constituent FFTs of the statistically representative spectrograph or spectrogram in such a manner as to emulate the result that would be produced by an EMI (Electromagnetic Interference) receiver or spectrum analyser; and combining resultant outputs from a number of iterations of this process to produce a final result (EMI spectrum).

Abstract: A variable speed drive for an electric motor has an inverter for receiving pulse width modulation controls. The inverter communicates power signals to a poly-phase electrical motor. A resolver communicates signals from the poly-phase motor back to a motor control. The motor control includes a speed control, a field-oriented control, and a pulse width modulation drive for driving the inverter. The resolver is connected to the speed control and to the field-oriented control, and further communicates with a synchronous compensator. The synchronous compensator is configured to drive the harmonic content at a target frequency or frequencies in a selected signal towards zero over time.

Abstract: A method of calibrating a robotic device, such as a cardiac catheter, includes oscillating the device on an actuation axis by applying an oscillation vector at an oscillation frequency. While oscillating, a location of the device is periodically measured to generate a plurality of location data points, which may express the location of the device relative to a plurality of measurement axes. The location data points are then processed using a signal processing algorithm, such as a Fourier transform algorithm, to derive a transfer function relating a position of the device to a movement vector for the actuation axis. The transfer function may be resolved into and expressed as a calibration vector for the actuation axis, which may include one or more components, including zero components, directed along each of the measurement axes. The process may be repeated for any actuation axes on which calibration is desired.

Abstract: A method determines a transient response of a sample. The method includes providing a measured magnitude of the Fourier transform of a complex electric field temporal profile of a pulse sequence comprising a first pulse indicative of the transient response of the sample and a second pulse. The method further includes providing an estimated phase term of the Fourier transform of the complex electric field temporal profile of the pulse sequence. The method further includes multiplying the measured magnitude and the estimated phase term to generate an estimated Fourier transform of the complex electric field temporal profile of the pulse sequence. The method further includes calculating an inverse Fourier transform of the estimated Fourier transform, wherein the inverse Fourier transform is a function of time. The method further includes calculating an estimated complex electric field temporal profile of the pulse sequence by applying at least one constraint to the inverse Fourier transform.

Abstract: Disclosed herein is a Fourier transform-based phasor estimation method and apparatus capable of eliminating the influence of exponentially decaying DC offsets. According to a Fourier transform-based phasor estimation method according to an embodiment of the present invention, an input signal is sampled, and samples of one-cycle data of the input signal are separated into at least two sample groups. A Discrete Fourier Transform (DFT) is performed on each of the sample groups. A DC offset included in the input signal is calculated on a basis of results of the DFT on each of the sample groups, and an error caused by the DC offset is calculated using the calculated DC offset. A phasor of a fundamental frequency component included in the input signal is estimated by eliminating the calculated error, caused by the DC offset, from the results of the DFT on the input signal.

Abstract: A method for evaluating data representing a plurality of excitations of a plurality of sensors; the method comprising: (a) storing the data as a plurality of entries in an information store; each respective sensor-excitation pair being a respective entry; (b) exercising a fit relationship employing at least one first sine value to determine a fit value substantially simultaneously for at least a portion of the plurality of entries; (c) ascertaining a measure of fit error between the data and the fit value for the portion of entries; (d) employing the measure of fit error to estimate at least one next sine value; (e) employing the at least one next sine value to perform a fit optimization operation with the data substantially simultaneously for the portion of entries; and (f) repeating steps (c) through (e) until a desired number of the sine values has been exercised.

Abstract: The invention as disclosed is of a method to authenticate identify and trace sonar transmissions and echoes by embedding transparent, secure and robust digital watermarks in signal space, where the additional information incurs no cost in bandwidth. The complex short time Fourier transform is selected as the domain for embedding the digital watermark, secured by a secret key, in the time frequency representation of the signal. The watermark is designed through an iterative optimization step. This step insures that the watermarked sonar is also realizable. Selection of the time frequency region for watermarking is driven by avoidance of interference with the sonar itself, or in case of network operation, other watermarks. In addition, the selected time-frequency region remains robust to sound channel and other transmission effects. Sonar echoes are authenticated in the time-frequency plane by a correlation receiver tuned to the watermarked region using the secret key.

Abstract: A method for determining characteristics of a multi-material object is provided. The method includes determining an electric element matrix representing the multi-material object. The electric element matrix is pre-multiplied by a first mathematical transformation matrix to obtain a first transformed electric element matrix. The first transformed electric element matrix is post-multiplied with a second mathematical transformation matrix to obtain a second transformed electric element matrix. The method further includes determining the characteristics of the multi-material object based on the second transformed electric element matrix.

Abstract: Provided is a dynamic balancing apparatus using a linear time-varying angular velocity model, which includes a rotational shaft on which a rotational body having a rotating unbalanced mass is installed; a linear time-varying angular velocity generator which allow the rotational shaft to be rotated at a linear time-varying angular velocity; a support for supporting both sides of the rotational shaft; and a transducer for measuring applied force or vibration transferred to the support by revolution of the rotational shaft having a linear time-varying angular velocity.

Abstract: The invention relates to a method for monitoring air pressure in vehicle tires using wheel electronics, which comprise a pressure sensor for measuring the air pressure present in the tire, a transmitter for transmitting pressure information, and a receiver for receiving interrogation signals, wherein a transmission activity of the wheel electronics is triggered by the reception of an interrogation signal, which is transmitted as a pulse train comprising a command section that encodes a transmission instruction for the wheel electronics. According to the invention, the pulse train comprises an adjustment section having several pulses before the command section.

Abstract: A method includes ascertaining harmonic components of a periodic analog signal at a fundamental frequency which changes over time. The signal is digitized and fast Fourier transformed. A target signal is produced by modulating the signal using a first carrier frequency to form two frequency sidebands, the first carrier frequency being greater than the fundamental frequency of the signal. One of the two frequency sidebands of the modulated signal is filtered. The filtered frequency sideband is modulated using a second carrier frequency forming two frequency sidebands. The second carrier frequency is greater than the fundamental frequency of the signal. The difference between the second and first carrier frequencies is the same as the difference between the fundamental frequency and the target fundamental frequency. One of these two frequency sidebands is output as the target signal to calculate the fast Fourier transformation.

Abstract: A method to predict a state of a power system and a device to perform the method are presented, where the method includes the step of performing a Fast Fourier Transform on samples of a periodic waveform signal in order to determine a frequency spectrum of the signal, where the signal was derived from at least one measurable electric quantity of the power system and is representative for the state of the power system. Frequencies and related complex amplitudes at selected peaks in the frequency spectrum are determined and stored together with a time stamp. Afterwards, a predicted value of the periodic waveform signal in the time domain is determined at a prediction time by calculating a sum of sinusoidal signals at the prediction time, where each of the sinusoidal signals is characterized by one of the determined frequencies and its related complex amplitude as well as the time stamp.

Abstract: A method and system for detecting a signal source at a specified frequency in the presence of background noise includes a processor; a first sensor mounted at a first location operatively connected to the processor; a second sensor mounted at a second location operatively connected to the processor; the processor operating to compute the amplitudes of the first and second Fourier transforms of the outputs of the first and second sensors, respectively, the difference in the amplitudes of the first and second Fourier transforms being determinative of the existence of a signal being generated at the predetermined frequency.

Abstract: A test and measurement instrument converts digital data that represents an input signal into a series of frequency spectra and accumulates frequency spectra into a bitmap database in response to a gating signal. In some embodiments, the gating signal is generated when the instantaneous power of the input signal violates a power threshold.

Abstract: A method utilizes an optical image processing system. The method includes providing a measured magnitude of the Fourier transform of a complex transmission function of an object or optical image. The method further includes providing an estimated phase term of the Fourier transform of the complex transmission function. The method further includes multiplying the measured magnitude and the estimated phase term to generate an estimated Fourier transform of the complex transmission function. The method further includes calculating an inverse Fourier transform of the estimated Fourier transform, wherein the inverse Fourier transform is a spatial function. The method further includes calculating an estimated complex transmission function by applying at least one constraint to the inverse Fourier transform.

Abstract: A first amplifier is arranged to receive a first signal from a first bus terminal. A second amplifier is configured to receive a second signal from a second bus terminal. An inverter input of an inverter is coupled to the output of the first amplifier. An input or inputs of an analog-to-digital converter are coupled to an inverter output of the inverter and the output of the second amplifier. The analog-to-digital converter is capable of producing a digital signal representative of the signals received from the first bus terminal and the second bus terminal. A data processor is capable of receiving an output of the analog-to-digital converter. The data processor is configured to apply one or more frequency domain transforms to the digital signal. The data processor identifies a circuit location of the ground fault or degraded isolation, a type of ground fault, or both based on the application of the frequency domain transform.